Ultra long-term sodium balance studies during the Mars500 campaign
- Paper number
IAC-12,A1,8,5,x16036
- Author
Mrs. Kathrin Jüttner, Germany
- Coauthor
Dr. Natalia Rakova, Germany
- Coauthor
Dr. Anke Dahlmann, Germany
- Coauthor
Dr. Manfred Rauh, Germany
- Coauthor
Mrs. Ulrike Goller, Germany
- Coauthor
Mr. Luis Beck, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Germany
- Coauthor
Dr. Agureev Alexander, Russia
- Coauthor
Dr. Galina Vasylieva, RF SRC - Institute of Biomedical Problems of the RAS, Russia
- Coauthor
Mrs. Liubov Lenkova, Russia
- Coauthor
Dr. Bernd Johannes, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Germany
- Coauthor
Dr. Peter Wabel, Germany
- Coauthor
Dr. Ulrich Moissl, Germany
- Coauthor
Prof. Jörg Vienken, Germany
- Coauthor
Prof. Rupert Gerzer, Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR), Germany
- Coauthor
Prof. Kai-Uwe Eckardt, Germany
- Coauthor
Prof. Dominik Müller, University of Erlangen, Germany
- Coauthor
Prof. Karl Kirsch, Germany
- Coauthor
Dr. Boris Morukov, Institute for Biomedical Problems, Russia
- Coauthor
Prof. Friedrich C. Luft, Germany
- Coauthor
Dr. Jens Titze, Germany
- Year
2012
- Abstract
Background: A direct relationship between salt intake and blood pressure is widely accepted. However, the relationship between changing salt intake, salt excretion, and total-body sodium (TBNa) is inferred but not known. Without such basic knowledge, the mechanisms leading to the blood pressure elevation cannot be determined. Purpose: We tested the hypothesis whether or not long-term dietary salt restriction from 12g/day to 9g/day and 6g/day significantly lowers blood pressure in healthy volunteers during the Mars500 campaign. We sought to perform long-term balance studies to monitor sodium retention, sodium losses, TBNa and their relationships to any changes in blood pressure. Methods: We investigated daily Na+ balance and blood pressure in crewmembers participating in the Mars500 campaign, a simulated space flight to Mars. The normal young men lived in the Mars500 simulator in a completely self-sustaining, thermoconstant environment for 105 and 520 days, and consumed a diet with a salt content of 12 g per day for the first 40 days of the study, which then was gradually decreased to 9 g per day for the 2nd third, and for to 6 g per day for the 3rd third of the isolation period. The longer duration of the 520-day study allowed re-exposition to the original 12 g salt intake level. Results: Reduced salt intake lowered blood pressure in the subjects; with reexposition, blood pressure increased to initial levels. The blood pressure-lowering effect of reduced salt intake was uncoupled from changes in sodium balance, while increased and decreased potassium balance reflected low- and high-salt intake respectively. Salt balance, body weight, extracellular fluid, and TBNa were independent of salt intake. Ultra long-term constancy in salt intake did not lead to a constant urinary sodium excretion, although salt excretion over each diet period was 90-95% of intake. Infradian rhythms in urinary sodium excretion were found, which were independent of salt intake, but dependent on urinary aldosterone excretion. These rhythms seemed to be synchronized with night-shift work during the Mars105 day study. Conclusions: We conclude that even moderate salt reduction induces relevant blood pressure decrease in healthy & normotensive subjects. The findings on day-to-day sodium balance must recast thinking about how homeostasis of internal environment composition and blood pressure are achieved. The findings will lead to novel studies of long-term salt regulation and disposition that could have mechanistic value concerning the blood pressure-related effects.
- Abstract document
- Manuscript document
(absent)